A variety of security articles are known in the art. For example, U.S. Pat. No. 5,169,707 (Faykish et al.) discloses a retroreflective security article with dual level verification. Included are primary legends that are visible under both ordinary diffuse lighting conditions and under retroreflective lighting conditions, and "retrolegends" that are viewable only under retroreflective viewing conditions. Thus, the primary legend provides a first level of screening or verification under ordinary diffuse lighting conditions, without special equipment. The retro-legends provide a second level of verification under retroreflective lighting conditions, and thus a higher degree of security for the article as a whole. Although the security articles disclosed in the '707 patent have their own utility, they share certain limitations. Specifically, the primary legend remains visible under retroreflective lighting conditions, which can obscure the retro-legends. Also, the articles disclosed in the '707 patent are necessarily transparent, so that they may be used over documents such as driver's licenses, title documents, and passports.
Another conventional security article is disclosed in U.S. Pat. No. 4,368,979 (Ruell) discloses an automobile identification system including a license plate having alpha-numeric characters perceptible to the unaided eye, and a hologram that provides encoded identifying information that cannot be decoded by the unaided eye. Although this, too, can be a useful product for some applications, the fact that an unaided eye cannot decode the holographic information renders the system more expensive, and correspondingly less useful for some applications.
In view of the disadvantages associated with these and other known articles, such as those disclosed in U.S. Pat. Nos. 3,993,401 (Strehlow), 4,036,552 (Lee et al.), and 4,095,875 (Lee et al.), it is desirable to provide an article having both holographic and retroreflective features, wherein the hologram does not visually interfere with the retroreflective feature.